The present invention relates generally to fuel pumps for vehicles and, more particularly, to multi-stage internal gear fuel pump for a vehicle.
It is known to provide a fuel tank in a vehicle to hold fuel to be used by an engine of the vehicle. It is also known to provide a fuel pump to pump fuel from the fuel tank to the engine. Examples of such fuel pumps are mechanically or electrically driven piston pumps, turbine pumps, gear pumps and mechanically, electrically or hydraulically driven diaphragm pumps. Some of the pumps used in systems for direct injection of volatile fluids such as gasoline are cam driven or crankshaft/connecting rod mechanism pumps. These pumps require a driving shaft and dynamic seals to prevent fuel leakage outside a pump housing or fuel to penetrate into a lubricated driving mechanism area. These pumps also require a shaft coupling a pump driving shaft with a source of rotational movement (e.g., engine crankshaft, camshaft). Some of these driving sources impose a specific location for the pump in the engine compartment. Dynamic sealing systems are usually expensive and do not guarantee an extensive leak free working life that meets fuel emission requirements for modern engines.
Engine driven pumps for direct injection systems also require an additional lift or prime pump to supply fuel from the fuel tank to the engine driven pump thereby increasing system cost. Pumps that are engine driven also have difficulty achieving pressure during vehicle starting conditions since rotational speed is typically below ideal pump speed thus resulting in starts under less than ideal conditions. This could lead to degraded start performance and higher emissions. Further, piston type engine driven pumps typically utilize drain and re-circulation lines to contain leak and dissipate heat, respectively, adding to cost and complexity.
For high pressure applications, such as gasoline direct injection operating at 5 MPa, attempts to use electrically driven single-stage internal gear pumps usually results in low efficiency-high power requirements. High leakage between gear teeth and gear faces reduces efficiency at high operating pressure necessitating the need for very tight tolerances. Tight tolerances usually result in high cost and poor durability.
Therefore, it is desirable to provide a pump that can be used for pumping volatile or non-volatile fluids for a vehicle. It is also desirable to provide a fuel pump for a vehicle that has an electrical driving mechanism contained within a common housing, eliminating the need for additional prime or lift pumps. It is further desirable to provide a fuel pump that eliminates any source of fluid leak for a vehicle and is able to provide adequate flow at desired pressure during vehicle starting conditions. Additionally, it is desirable to provide a pump that can be mounted either in a fuel line or fuel tank. It is still further desirable to provide a pump not requiring drain or re-circulating lines. It is also desirable to provide a pump that can be modular in design so that pumping sections can be added to reduce sectional pressure differential and provide for operation at higher pressure and efficiency at nominal tolerance levels.
It is, therefore, one object of the present invention to provide a multi-stage internal gear fuel pump for a fuel tank or for xe2x80x9cin-linexe2x80x9d mounting in a vehicle.
It is another object of the present invention to provide a multi-stage internal gear fuel pump for a vehicle that provides a driving mechanism completely contained within a pump housing.
It is yet another object of the present invention to provide a multi-stage internal gear fuel pump for a vehicle that provides high discharge fuel pressure to satisfy requirements of a gasoline direct injection fuel system.
To achieve the foregoing objects, the present invention is a multi-stage internal gear fuel pump for a vehicle including a housing having an inlet and an outlet and a motor disposed in the housing. The multi-stage internal gear fuel pump also includes a shaft extending axially and disposed in the housing for rotation by the motor. The multi-stage internal gear fuel pump further includes a plurality of pumping modules disposed axially along the shaft and each having an internal gear and an external gear cooperating with each other for rotation by the motor to pump fuel from the inlet to the outlet.
One advantage of the present invention is that a multi-stage internal gear fuel pump is provided for a vehicle. Another advantage of the present invention is that the multi-stage internal gear fuel pump is low cost, simple construction and eliminates the need for expensive dynamic shaft seals. Yet another advantage of the present invention is that the multi-stage internal gear fuel pump eliminates the need for mechanical coupling with a driving device. Still another advantage of the present invention is that the multi-stage internal gear fuel pump can be placed in the fuel line near the fuel tank or located in the fuel tank. A further advantage of the present invention is that the multi-stage internal gear fuel pump incorporates a high speed DC electrical motor, allowing a quick priming of the pump and fast pressure/flow generating and eliminating the need for lift or prime pumps. Yet a further advantage of the present invention is that the multi-stage internal gear fuel pump is compact, modular and easy to assembly. Still a further advantage of the present invention it that the multi-stage internal gear fuel pump incorporates a plurality of modular pumping sections, allowing output pressure to be increased to a required value of direct injection fuel systems. Another advantage of the present invention is that the multi-stage internal gear fuel pump incorporates integral pressure regulation or pressure by feedback-speed control which simplifies the system to a single line supply typically called return-less or demand supply.
Other objects, features, and advantages of the present invention will be readily appreciated, as the same becomes better understood, after reading the subsequent description taken in conjunction with the accompanying drawings.